Every car owner notices that the appearance of the car consists of many small details that at first glance seem secondary. One of these elements is the edging around the windshield, which professionals call molding. This is not just a decorative bar, closing the joint between the body and glazing, but an important functional unit that ensures tightness and aerodynamics.
Over time, even the best quality sealer It can lose its properties, and the edge itself - move away from the surface. Ignoring this problem often leads to cabin leaks during rain or the appearance of a wind whistle at high speeds. In this material, we will discuss in detail why the molding is peeled off, what materials are used for its fixation and how to properly carry out restoration work with your own hands.
Functional purpose and arrangement
At first glance, it may seem that the only purpose of this element is aesthetic. Indeed, the black edging hides the sealant seam of the factory, making the transition from the body metal to the glass visually pleasant and smooth. However, if you look deeper, it becomes clear that molding It plays a much more important engineering role in the design of the body.
The main function is to protect the adhesive seam from the aggressive effects of the external environment. Ultraviolet radiation, temperature changes, road reagents and moisture can quickly destroy the polyurethane layer if it is not closed. That is why the presence of a whole edging directly affects the durability of the glass installation.
In addition, this element improves the aerodynamic properties of the car. A properly installed bar directs air flows and running water so that they do not fall into the area of work of janitors and do not create unnecessary noise. In some modern models Toyota or BMW The edging profile is specially calculated in the wind tunnel to reduce the drag coefficient.
⚠️ Attention: The use of non-original moldings with disturbed geometry can lead to a whistle in the cabin at speeds above 90 km / h and accelerated wear of wiper brushes.
When buying a used car, carefully examine the junction of glass and body: the presence of traces of fresh sealant or carelessly glued edging may indicate a recently carried out replacement of the windshield.
Types of edging and materials of manufacture
Automakers use different approaches to the design of the glazing perimeter, and the choice of material depends on the class of the machine and the structural features of the body. Understanding the type of your molding is necessary for the correct selection of adhesive composition during repair. Most often there are three main varieties of these elements.
The first type is rigid strips made of plastic or metal, which are attached to special latches or double-sided tape. They are typical for older generation cars or SUVs, where mechanical strength is important. The second type is soft rubber or polyurethane profiles, which are often glued together with the glass or glued separately after installation. The third option is a black ceramic paint applied directly to the glass with a texture that mimics molding, which is often found on modern budget models.
- 🚗 Chrome inserts - used in luxury configurations to give the car a premium look, require polishing along with the body.
- 🌧️ Rubber seals - a classic solution that provides excellent tightness, but is prone to drying out in the cold.
- 🖌️ Plastic linings The most common option, light and cheap to produce, but sensitive to stone impacts.
The materials from which these parts are made must have high elasticity and resistance to UV radiation. Cheap analogues from China often lose color after a year of operation, starting to burn out and become covered with microcracks. Quality plastic It retains its properties throughout the life of the vehicle.
Causes of unfettering and damage
The situation when the edging begins to move away from the body is familiar to many motorists, especially owners of cars with a mileage of more than 5-7 years. There are a number of objective reasons why this happens, and knowing them will help prevent a problem in the future or choose the right repair strategy.
The main enemy of any adhesive compound is moisture. If in the process of previous glass replacement the sealant application technology was violated, water can penetrate the edging, blurring the adhesive layer. This is especially true for regions with frequent washing under high pressure and harsh winter conditions, when water freezes in microcracks, expanding and tearing off the material.
The second factor is mechanical impact. Windshield wiper brushes in winter, when they try to catch up to the glass, can touch the lower part of the edging when trying to break them off. Also frequent trips on the track lead to blows of small stones and gravel, which violate the integrity of the structure of the material. In time. polyurethane It ages and loses adhesion, which is a natural wear and tear process.
⚠️ Warning: Attempting to forcefully tear off the wiper brush often leads to deformation of the lower molding, after which it cannot be restored without replacement.
Preparation for recovery and necessary tools
Before starting to stick the fallen off element, it is necessary to carefully prepare the surface. The quality of the final result depends on 90% of how well you clean the glue areas of old sealant, fat and dirt. Neglecting this stage will result in even the most expensive glue not holding.
To work, you will need a minimum set of tools that are found in the garage of most motorists. It is important to use only specialized chemical compounds designed for cars, as household adhesives can not withstand vibrations and temperature changes. It is also worth taking care of hand protection, as some degreasers are aggressive to the skin.
☑️ Checklist of preparations
The list of required materials includes:
- 🧴 Degreaser (antisilicone or white spirit) - to remove bitumen stains and oil residues.
- 🔪 A stationery knife or scalpel - for neatly cutting off an old sealant.
- 🧽 Fine-grained sandpaper (P2000) – to create micro-scratch on smooth surfaces for better adhesion.
- 🔫 Sealant gun - if a tube with a polyurethane composition is used.
Pay special attention to the choice of glue. For rubber and plastic moldings, black polyurethane sealant glue, such as 3M or Teroson. It remains elastic after drying, which allows you to compensate for the vibrations of the body.
Step-by-step installation instructions
The process of restoration of tightness and fixation of the edging requires accuracy and compliance with the time intervals specified by the adhesive manufacturer. Do not rush, as polymerization of the composition is a chemical process that cannot be accelerated artificially without loss of quality.
First, the outgoing part must be completely dismantled. Remains of old glue from the body and the molding itself are removed mechanically. If there are traces of corrosion on the metal, they must be cleaned and treated with a rust converter, otherwise the destruction process will continue under a new overlay.
Algorithm of action:1. Cleaning surfaces to metal/plastic.
2. Degreasing (2-3 passes with pure rags).
3. Applying a primer (if required by the instructions).
4. Applying a glue strip.
5. Fix and shutter.
After applying the adhesive composition, the element is installed in place. It is important to fix it immediately with paint tape or special clips to prevent slipping to the moment of initial grasping. The primary fixation time is usually 30 minutes to 2 hours, depending on air temperature and humidity.
Nuances of work in the cold season
If you are repairing in the garage at a temperature below +10 ° C, the time of polymerization of the adhesive increases by 2-3 times. It is recommended to preheat the body and the molding itself with a building hair dryer to room temperature, but not to overheat the plastic so as not to cause its deformation.
Complete drying and maximum strength gain occurs within 24 hours. During this period, it is not recommended to wash the car under pressure or go to high-speed highways.
Comparison of fixation methods
The choice of the method of fastening depends on the design of the particular car and the type of molding. Sometimes it is enough to use reinforced bilateral tape, and in other cases it is not possible to do without liquid polyurethane. Let’s look at the main differences in the table.
| Method | Strength | Difficulty in dismantling | Application |
|---|---|---|---|
| Polyurethane sealant | Tall. | Tall (knife needed) | Main pasting, glass repair |
| Double-sided 3M Scotch | Medium | Low. | Decorative pads, light moldings |
| Mechanical latching | Tall. | Medium | Factory installation, hard plastic |
As you can see from the table, there is no universal solution. For reliable sealing of the junction of glass and body is best suited to polyurethane composition, which creates a monolithic connection. Scotch is good only for fixing decorative elements that do not carry the load on moisture retention.
The main criterion for choosing adhesive is its elasticity after drying: hard glue will lead to detachment at the first vibration of the body or skewed body on the road.
Common mistakes in self-repair
Trying to save on the services of a car service, owners often make mistakes that lead to the need to redo the work. The most common of these is poor surface cleaning. Dust, invisible to the eye, creates a barrier between the glue and the surface, drastically reducing adhesion.
Another common mistake is the use of “superglue” or other household cyanacrylate formulations. These substances, after solidification, become hard and brittle. The body of the car is constantly vibrating and slightly “breathing” when temperatures change, so the glue should work as a shock absorber. The hard glue will just crack and the molding will fall off.
Also, do not ignore the recommendations on drying time. The desire to remove the fixing tape faster often leads to the displacement of the element. If the adhesive seam is broken during the solidification process, its sealing properties will be lost irretrievably.
⚠️ Warning: Never use acid silicone sealants (the ones that smell like vinegar) to paste body elements – they cause metal corrosion and break down some types of plastic.
When is the best time to talk to professionals
Despite the apparent simplicity of the operation, there are situations when self-repair is not advisable. If the windshield itself is damaged or there is a suspicion of a displacement of the geometry of the body after an accident, it is better to entrust the work to specialists. They have the necessary equipment to calibrate safety systems, which are often tied to the windshield.
Professional replacement or restoration of molding includes not only the application of glue, but also checking the condition of the drainage grooves, cleaning the drainage holes and testing for leakage with a jet of water under pressure. This ensures that the cabin will be dry even in the strongest rain.
In addition, specialized services provide a guarantee for their work. If after a month the edging begins to move away again, you will be corrected the defect for free. In the case of self-repair, all the risks and costs of re-constitution fall solely on your shoulders.
Can I glue the molding with ordinary silicone?
It's not recommended. Conventional construction or sanitary silicone does not have the necessary adhesion to automotive plastics and metal in conditions of constant vibration. It may also contain components that cause corrosion.
How much does a car sealant dry?
Primary grip occurs in 30-60 minutes, but the full strength and water resistance of the composition gains after 12-24 hours. The exact time is always indicated on the packaging of a particular product.
Do I need to remove the molding completely to replace the glass?
In most modern cars, when replacing the windshield, the old molding is cut off along with the sealant. The installation is made with a new set of edging, as the old deforms and loses geometry.
How to degrease the surface before gluing?
It is best to use specialized car degreasings (antisilicons). White spirit is also suitable, but gasoline or acetone is best avoided, as they can damage the structure of the plastic or paint coating.